Method for producing a measuring electrode suitable for electrochemical measurements with a force-fitting shrink tube contact in the hollow tubular body and measuring electrode contacted in this way

Abstract

Method for producing a measuring electrode for electrochemical measurements in a measuring fluid, in which (a) a sensor material body (5), from which a line piece (6) made of electrically conductive material, which is electrically conductively connected to the sensor material body (5) protrudes, is joined to the tubular body (1) so that the line piece (6) protrudes into the tubular body (1) in the joined state, (b) a connecting cable (7) made of electrically conductive material is inserted into the pipe body (1) until it overlaps with the cable piece (6), and (c) the connecting cable (7) is connected in the overlap in a force-fitting electrically conductive manner to the cable section (6), (d) wherein a shrink tube (8) is inserted into the pipe body (1) so that the shrink tube (8) surrounds the line piece (6) and the connecting line (7) in the overlap, and (e) the shrink tube (8) is shrunk so that the shrunk shrink tube (8) presses the cable piece (6) and the connecting cable (7) together lengthwise and thereby connects them in a force-fitting, electrically conductive manner.

Description

[0001] The invention relates to measuring electrodes for electrochemical measurements in measuring fluids and methods for the production of measuring electrodes. In particular, the invention relates to redox electrodes and methods for their production. In addition, the invention also relates to other types of measuring electrodes, for example chlorine electrodes, hydrogen peroxide (H 2 O 2 ) electrodes, corrotrodes, titration electrodes and other types of measuring electrodes for potentiometric or amperometric measurements.

[0002] DE 10 2012 101 004 A1 discloses a reference electrode for use in electrochemical measuring systems. The electrode comprises a housing with a chamber filled with an electrolyte, in which a potential-forming element is arranged so that the electrolyte wets the potential-forming element. To conduct the potential, an electrical conductor is connected to the potential-forming element; it is mentioned that a shrink tube can serve as a connection point.

[0003] EP 0 171 959 A2 discloses an electrode with a sensor element made of antimony and antimony oxide. The sensor element is connected to a connecting lead via a graphite filament conductor. The graphite filaments are wound around the sensor element or coated with the sensor element material, thereby electrically connecting it to the sensor element at one end. At the other end, the graphite filament conductor is connected to the connecting lead. For insulation purposes, a shrink tube surrounds the section where the sensor element is connected to the conductor.

[0004] The CN 101 419 185 A discloses a CO 2 Electrode in which a connecting lead is soldered to a sensor material body. A shrink tube surrounds the solder joint and an adjacent section of the connecting lead.

[0005] Other measuring electrodes used for electrochemical measurements have a tubular body made of glass or plastic and a sensor material body arranged on the tubular body. The sensor material body is usually arranged at one end of the tubular body. The sensor material body is electrically connected to a connection area of ​​the measuring electrode through the hollow tubular body by means of a connecting line. Such measuring electrodes are disclosed, for example, in the generic DE 20 2011 101 241 U1. During production of the measuring electrode, the sensor material body and the connecting line are connected to one another in a first step. The connecting line is then threaded through an opening in a tubular body blank. In a further step, the sensor material body is joined to the tubular body blank in the region of the opening, for example by melting the sensor material body.The manufacture of the joint between the sensor material body and the tube body is problematic due to the typically thin and / or flexible connecting cable that must be threaded into the tube body blank. Therefore, such measuring electrodes are manufactured using manual labor.

[0006] It is an object of the invention to further automate the production of generic measuring electrodes and to propose a measuring electrode that can be produced with an increased degree of automation.

[0007] The object is achieved by the subject matter of claim 1. Claim 5 describes a measuring electrode according to the invention.

[0008] The invention relates to a method in which a sensor assembly comprising a sensor material body and a line piece is provided or produced in the method. The line piece is electrically conductively connected to the sensor material body and protrudes from it on a rear side. The sensor material body is joined to the tubular body so that the line piece protrudes into the tubular body in the joined state. A connecting line made of electrically conductive material is inserted into the tubular body until it overlaps with the line piece. The connecting line is connected to the line piece in a force-fitting, electrically conductive manner in the overlap.

[0009] The invention relates to a method in which a sensor assembly comprising a sensor material body and a line piece is provided or produced in the method. The line piece is electrically conductively connected to the sensor material body and protrudes from it on a rear side. The sensor material body is joined to the tubular body so that the line piece protrudes into the tubular body in the joined state. A connecting line made of electrically conductive material is inserted into the tubular body until it overlaps with the line piece. The connecting line is connected to the line piece in a force-fitting, electrically conductive manner in the overlap.

[0010] The invention is also directed to a measuring electrode suitable for electrochemical measurements in a measuring fluid, which comprises a tubular body, a sensor material body arranged on the tubular body, and a connecting line electrically connected to the sensor material body. The sensor material body can in particular be arranged at a front end of the tubular body. The tubular body can be, for example, a plastic body or preferably a glass body. The sensor material of the sensor material body can be a metal, such as titanium, vanadium, tungsten, or stainless steel, and in particular a precious metal, preferably platinum or gold. The sensor material body can consist of the metal. The connecting line extends in the tubular body. It electrically connects the sensor material body to a connection area of ​​the measuring electrode. The connection area serves to connect the

[0011] Measuring electrode to an external operating device, for example a measuring device, monitoring device, control device or control device.

[0012] According to the invention, the sensor material body is provided with a line piece for dissipating the electrical potential of the sensor material body. The line piece is electrically conductively connected to the sensor material body and projects from a rear side of the sensor material body into the tubular body. The connecting line overlaps with the line piece in the tubular body in the longitudinal direction and is connected to the line piece in the overlapping area in an electrically conductive, expediently tensile-resistant, manner. Due to the division of the electrical connection into a connecting line and a line piece projecting from the sensor material body into the tubular body, which can be significantly shorter than the connecting line, the joining of the sensor material body and the tubular body is facilitated. When positioning the sensor material body and the tubular body, there is no need for a comparatively long and correspondingly flexible orA flexible connecting cable can be threaded through a narrow opening in the tubular body in order to join the sensor material body to the tubular body when the connecting cable is threaded in. The invention makes it easier or even makes it possible for the first time to automate the joining process, including the insertion of the cable section. Due to its short length, with which it protrudes from a rear side of the sensor material body, the cable section is so stiff that when the sensor material body is positioned at the opening in the tubular body, the cable section is positioned at the same time, i.e. it protrudes into the tubular body. The cable section does not have to be positioned specifically for joining, for example by being laboriously threaded through the opening in the tubular body. The cable section can protrude from a rear side of the sensor material body, in particular orthogonally to the rear side.

[0013] Because of the frictional connection, a material-to-material connection is no longer necessary. Soldered and welded connections have been common practice so far. When the sensor material body and the connecting cable are made of different materials, soldered connections are more common. Soldered and sometimes welded connections are cumbersome because not only the respective sensor material body and the connecting cable but also the solder or welding material must be fed and positioned to connect them. The frictional connection allows for flexible material selection. For example, the cable section can be made of a first metal and the connecting cable of a different, second metal. It is practical if the cable section is made of platinum or gold and the connecting cable of a cheaper precious metal, such as silver.When reference is made to “metal” or a specific metal, this also includes metal alloys containing the respective metal as the base metal.

[0014] The frictional connection is created by means of a shrink tube that surrounds the cable section and / or the connecting cable in the overlap and, when shrunk, creates an electrically conductive connection in the frictional connection.

[0015] The heat shrink tubing can be formed or attached to the cable piece or instead to the connecting cable, so that the cable piece with its heat shrink tubing can be pushed onto a facing end of the connecting cable or instead the connecting cable with its heat shrink tubing can be pushed onto a facing end of the cable piece and shrunk in the pushed-on state.

[0016] Preferably, the frictional connection is achieved by means of a heat-shrinkable sleeve, which is provided in addition to the cable section and the connecting cable. In the overlap, the cable section and the connecting cable are in longitudinal contact and are pressed together by the shrinkable heat-shrinkable sleeve, which surrounds the cable section and the connecting cable in the overlap area, thus securely holding them in contact.

[0017] The invention offers further advantages in terms of manufacturing: the contacting can be automated and carried out more easily by frictional connection than by welding or soldering the cable section and the comparatively long connecting cable. Another advantage is that the shrinking process can be carried out simultaneously in a furnace with multiple assemblies, each consisting of a tubular body and a joined sensor material body.

[0018] A fully automated production of the measuring electrode comprises the provision of a sensor assembly consisting of a sensor material body and a line piece and the joining of the sensor assembly and the tube body. In the method, a first gripper positions the sensor material body on a joining receptacle. The sensor material body is fixed to the joining receptacle by means of suction force. The sensor material body can rest against the joining receptacle with a front side and be sucked onto the joining receptacle at the front. The joining receptacle expediently has a system for the sensor material body and, in the region of the system, a suction opening for sucking in the sensor material body. In a further step, a second gripper positions a line piece relative to the fixed sensor material body; preferably, the second gripper positions the line piece on, i.e. in contact with, the fixed sensor material body.In a further step, the positioned cable piece is electrically connected to the fixed sensor material body by means of a joining tool.

[0019] The sensor assembly consisting of the sensor material body and the line piece is joined to the tubular body. The tubular body is provided with a front opening in the front area of ​​the tubular body. For joining, the sensor assembly and / or the tubular body is / are positioned relative to one another in a joining position. During joining, the tubular body is held by means of a chuck, advantageously in a horizontal orientation. In the joining position, the rear side of the sensor material body faces the front opening of the tubular body, and the line piece protrudes through the opening into the tubular body. In the area of ​​the opening, the tubular body is connected to the sensor material body in a fluid-tight manner around the opening by means of a fusion bond and / or a material bond. The material bond can be an adhesive bond, for example. The fusion bond can involve a direct material bond between the sensor material body and the tubular body.

[0020] The assembly consisting of the tubular body and the sensor assembly thus obtained can, as previously explained, be supplemented by the connecting cable, whereby the contacting by means of force-locking can follow as part of a continuous sequence of steps or only after an intermediate storage of the assembly consisting of the tubular body and the sensor assembly.

[0021] As far as the sensor assembly is concerned, the lead piece can be butt-fitted with one end to the rear of the sensor material body and joined to the sensor material body at the end by a material-to-material bond. More preferably, the lead piece is electrically conductively connected to the sensor material body in a first lead section and comprises a second lead section that is inclined toward the first lead section and protrudes from a rear side of the sensor material body. The lead piece can be placed lengthwise against the rear side of the sensor material piece, fixed in this relative position, and joined to the sensor material body in the region of the applied first lead section by means of a joining tool in a material-to-material bond, thus making it electrically conductive and mechanically secure.The second line section can be erected in the applied state before, during or, more preferably, after joining relative to the sensor material body so that it points at least substantially orthogonally to the back of the sensor material body.

[0022] The sensor assembly consisting of the sensor material body and the lead piece can be umbrella-shaped or nail-shaped.

[0023] Regarding the measuring electrode, it should be added that the tubular body may have an outer tube, an inner tube surrounded by the outer tube, an inner cavity surrounded by the inner tube, in which the connecting cable extends and into which the cable piece projects, and an outer cavity surrounding the inner tube and surrounded by the outer tube for a reference electrode.

[0024] The tube body can in particular be a glass tube body, preferably a multi-walled glass tube body.

[0025] The sensor material body, the line piece and the connecting line can consist at least substantially of electrically conductive material, preferably of metal.

[0026] The sensor material body and / or the lead section may be made of platinum or a platinum-based alloy. The connecting lead is preferably made of silver or a silver-based alloy.

[0027] The measuring electrode can advantageously be a redox electrode, chlorine electrode, hydrogen peroxide electrode, corrotrode or titration electrode.

[0028] When using the auxiliary tool, the connecting cable and the heat-shrink tubing are advantageously inserted into the tubular auxiliary tool, and the auxiliary tool, together with the connecting cable and the heat-shrink tubing, is inserted into the tubular body and moved toward the cable section. This causes the connecting cable and the heat-shrink tubing to overlap with the cable section.

[0029] It is advantageous if the auxiliary tool surrounds the shrink tube with frictional contact when it is inserted into the pipe body and thus holds it.

[0030] The shrink tube may protrude longitudinally beyond the auxiliary tool when inserted into the pipe body.

[0031] The tubular body can guide the auxiliary tool axially during insertion.

[0032] The assembly of tube body, sensor material body, cable piece, connecting cable and heat shrink tubing as well as optional auxiliary tools can be heated in an oven and the heat shrink tubing shrunk so that the heat shrink tubing presses the cable piece and the connecting cable together lengthwise and thereby creates a force-fit electrically conductive connection.

[0033] An exemplary embodiment of the invention is explained below with reference to the figures. The features revealed in the exemplary embodiment, individually and in any combination of features, advantageously develop the subject matter of the claims and the embodiments described above. They show: Fig. 1 a measuring electrode with a tubular body and a sensor material body, which is contacted with a connecting cable via a cable piece, Fig. 2 a front tubular body area with the joined sensor material body and a contact area of ​​the line piece and connecting line, Fig. 3 the sensor material body with the joined line piece, Fig. 4 a first gripper during positioning of the sensor material body on a joining holder, Fig. 5 a second gripper when positioning the cable piece on the sensor material body, Fig. 6 a joining tool when joining the cable piece and the sensor material body, Fig. 7 shows the interaction of the second gripper and the joining tool when aligning the cable piece relative to the sensor material body, Fig. 8 a transfer of the sensor assembly consisting of sensor material body and cable piece to a third gripper, Fig. 9 positioning of sensor assembly and pipe body for joining, Fig. 10 a melting device when joining the tube body and sensor assembly, Fig. 11 the insertion of the connecting cable and a shrink tube into the pipe body, Fig. 12 the shrink tube and an auxiliary tool and Fig. 13 the auxiliary tool in a position inserted into the pipe body in which the connecting cable overlaps the cable piece lengthwise and is surrounded by the heat shrink tubing in the overlap.

[0034] Fig. Figure 1 shows a measuring electrode, for example, a redox electrode, in a longitudinal section. The measuring electrode is part of a single-rod measuring chain, which includes the measuring electrode and a reference electrode in an integrated design. The reference electrode is not shown. Fig. 1 shows only the container for an electrolyte and a discharge system for the reference electrode. The measuring chain further comprises a connection device via which the measuring chain can be connected to a display device, monitoring device, or other external operating device related to the measuring chain.

[0035] The measuring electrode comprises a tubular body 1, which is double-walled to maintain the single-rod measuring chain with an outer tube 2 and an inner tube 3. The inner tube 3 surrounds an inner cavity H ı . The outer tube 2 surrounds the inner tube 3 and an outer cavity H A , which is internally bounded by the inner tube 3. The outer cavity H A serves to hold the electrolyte and the conduction system of the reference electrode. It is ring-shaped and closed in the front tubular body area. The tubular body 1 is closed at its rear end via both cavities H I and H Aopen and is closed there with the connection device after the reference electrode has been completed.

[0036] The connection device therefore serves not only for the electrical connection of the measuring and reference electrodes, but also for the closure of the tubular body 1.

[0037] A sensor material body 5 is arranged in the front tubular body region, in this embodiment at the front end of tubular body 1. The sensor material body 5 is fused into the material of tubular body 1 and / or remelted with the tubular body material, i.e., joined to tubular body 1 by means of a fusion bond. The sensor material body 5 forms the front end of the measuring electrode in the form of a measuring tip. It is made of a metal, preferably platinum or gold, or for example, silver or titanium. As already mentioned at the beginning, this also includes corresponding metal alloys.

[0038] Fig. 2 shows the front tubular body area of ​​the measuring electrode in the same longitudinal section as Fig. 1. The melt connection is marked with S 1 At the inner cavity H I facing rear side, a wire-shaped line piece 6 protrudes from the sensor material body 5 into the cavity H IThe electrical potential of the sensor material body 5 is conducted via the line section 6 and a connecting line 7 to the connection device of the measuring electrode, in the exemplary embodiment of the single-rod measuring chain. The connecting line 7 extends from the rear region of the tubular body 1 in the longitudinal direction through the inner tube 3 to a longitudinal overlap with the line section 6. In the overlap, the line section 6 and the connecting line 7 are connected in a frictional connection in an electrically conductive and mechanically sufficiently strong manner. The frictional connection is created by means of a shrink tube 8, expediently a plastic shrink tube. The shrink tube 8 surrounds the line section 6 and the connecting line 8 in the area of ​​the overlap and, in the shrunken state, presses the line section 6 and the connecting line 8 against one another lengthwise.It is advantageous if the shrink tube 8 extends a little way beyond the overlap to the rear, as in the exemplary embodiment, only surrounding the connecting cable 7.

[0039] The line section 6 protrudes only over a comparatively small length into the cavity H I in. With L 6 is the length with which the line piece 6 protrudes from the sensor material body 5, ie it is the length L 6 , which is measured from the free end of the line piece 6 to the back of the sensor material body 5. The length L 6 is several times smaller than a length L 1 of the pipe body 1. The length L 1 is measured from the rear end of the tube body 1, here from the rear end of the inner tube 3, to the sensor material body 5. The length L 1 is advantageously more than five times or more than ten times greater than the length L 6. It is advantageous for the contact and tensile strength of the force connection if the length L 6 at least 4 mm or at least 6 mm. On the other hand, a short length facilitates insertion into the pipe body 1 during joining, so that a length L 6 of less than 40 mm or, more preferably, less than 30 mm is advantageous.

[0040] In Fig. Figure 3 shows the sensor assembly consisting of sensor material body 5 and lead piece 6 in the assembled state in a central longitudinal section. The sensor material body 5 is cup-shaped and convex when viewed from its front side. The sensor material body 5 can, for example, be a spherical or hollow spherical cap. The lead piece 6 protrudes from the concave rear side orthogonally to the rear side. Figuratively speaking, the sensor assembly 5, 6 has the shape of a thumbtack or umbrella.

[0041] In Fig. 3 is also the length L 6with which the lead piece 6 protrudes from the back of the sensor material body 5. D 5 denotes the greatest width of the sensor material body 5, ie the greatest extension of the sensor material body 5 transverse to the longitudinal axis L. In expedient embodiments, the length L 6 less than six times or less than three times the width D 5 .

[0042] The line section 6 is connected in a first line section 6a by means of a material connection S 2 electrically conductively and mechanically firmly connected to the sensor material body 5. The line piece 6 protrudes freely from the sensor material body 5 with a second line section 6b. A short transition section connects the line sections 6a and 6b, which point at an angle to one another (in the exemplary embodiment, at an acute angle).

[0043] The conductor section 6 is also made of a precious metal or a precious metal alloy. Advantageously, it is at least essentially the same material as the sensor material body 5. The material bond S 2 is a welded connection directly between the sensor material body 5 and the line piece 6. If the sensor material body 5 and the line piece 6 are not made of identical materials, the materials are at least similar in advantageous embodiments to the extent that they can be welded directly, ie without weld metal.

[0044] The Fig. 4 to 13 illustrate steps of a method for manufacturing the measuring electrode, the order of the figures corresponding to the sequence of the method.

[0045] In steps not shown, which precede the respective measuring electrode, sensor material bodies 5 and conductor pieces 6 are obtained. A conductor wire is unwound from a wire reel and cut to the length of the respective conductor piece 6. The sensor material body 5 is obtained by separating and forming a strip material. For this purpose, a punching tool can also be designed as a deep-drawing die, so that the sensor material bodies 5 are punched directly from the strip material during the deep-drawing process.

[0046] As in Fig. 4, the sensor material body 5 is moved by a first gripper 11 to a joining receptacle 10 and placed against the joining receptacle 10, for example, placed in the joining receptacle 10. The first gripper 11 is a suction gripper that holds the sensor material body 5 at its rear side using suction force during handling. For this purpose, a vacuum line 17 opens at one end of the first gripper 11. The gripper 11 picks up the respective sensor material body 5 at its rear side with this gripper end. The front side of the sensor material body 5 remains free, so that the sensor material body 5 can very easily be placed with its front side against the joining receptacle 10. The sensor material body 5 is also held on the joining receptacle 10 using suction force. A vacuum line 18 therefore opens at a contact surface provided for the sensor material body 5, via which the sensor material body 5 is sucked in and thereby fixed to the joining receptacle 10.The contact surface is shaped complementarily to the front surface of the sensor material body 5.

[0047] Fig. 5 shows the joining receptacle 10 with the received sensor material body 5, which is subjected to negative pressure via the vacuum line 18 and thereby fixed to the joining receptacle 10. A second gripper 12 holds a line piece 6 in a clamping engagement and positions the line piece 6 longitudinally on the rear side of the sensor material body 5 fixed to the joining receptacle 10.

[0048] In Fig. 6, the cable section 6 is in the joining position on the sensor material body 5. The gripper 12 holds the cable section 6 in the joining position. For joining, a joining tool 20, in the exemplary embodiment a welding tool, is pressed against the cable section 6 in the joining position in the area of ​​the first cable section 6a.

[0049] In pressure contact, the line piece 6 is directly connected to the sensor material body 5 by means of the joining tool 20, in the exemplary embodiment by direct welding, for example resistance welding.

[0050] To install the sensor assembly 5, 6 in the Fig. 3, the line piece 6, which is positioned on the back of the sensor material body 5 and has already been joined by a material bond, is erected relative to the sensor material body 5 by forming, such as bending or edging. This is expediently carried out by means of the second gripper 12, which remains in clamping engagement with the line piece during the joining and forming process. During the forming process, the line piece 6 in the first line section 6b is pressed against the sensor material body 5 and is thereby held down. The joining tool 20 can serve as a hold-down device during the forming process.

[0051] Fig. 7 shows the sensor assembly 5, 6 still in the joint holder after the material connection S has been established. 2 of sensor material body 5 and line piece 6 and immediately after erecting the line piece 6.

[0052] The forming and material-to-material joining process can also be designed in such a way that the line section 6 is first erected using the gripper 12 and then joined to the sensor material body 5 using the joining tool 20. The joining tool 20 would initially act only as a hold-down device. In another alternative process, the erection can be performed simultaneously with the material-to-material joining.

[0053] During the joining of the sensor material body 5 and the line piece 6 and during the forming of the line piece 6, the sensor material body 5 remains on or in the joining receptacle 10 and can be fixed thereto by means of suction force.

[0054] The sensor assembly 5, 6 obtained by forming and joining can be set down or even temporarily stored. It is preferably held by a gripper on the line section 6 and transferred to a third gripper for joining with a pipe body 1. The transfer can expediently be performed by the second gripper 12, which can maintain the clamping engagement with the line section 6 and remove the sensor assembly 5, 6 directly from the joining receptacle 10 and transfer it to the third gripper.

[0055] The handover is in Fig. 8. The third gripper 13 is a suction gripper that holds the sensor assembly 5, 6 at the front of the sensor material body 5 by means of suction force. The gripper 13 is therefore connected to a device for generating a vacuum via a vacuum line 19, which opens at a contact surface of the gripper 13. Once the sensor assembly 5, 6 has been picked up by the third gripper 13 by means of the vacuum application, the second gripper 12 releases the clamping engagement with the line section 6, so that the transfer to the gripper 13 is completed. The gripper 13 now holds the sensor assembly 5, 6 at the front of the sensor material body 5, and the line section 6 protrudes freely from the rear of the sensor material body 5.

[0056] To join the sensor assembly 5, 6 with a tubular body 1, the tubular body 1 in question is removed from a separating magazine for tubular bodies 1, moved into a joining position and held in the joining position.

[0057] The Fig. 9 and Fig. 10 show the joining of the sensor assembly 5, 6 with a tubular body 1, which is clamped in a chuck 15, in the exemplary embodiment a rotary spindle chuck, in a horizontal orientation. The tubular body 1 has a front opening 1a at its front end, relative to which the sensor assembly 5, 6 is positioned by means of the gripper 13 such that the rear side of the sensor material body 5 is axially opposite the opening 1a and the line piece 6 is inserted into the tubular body 1, in the exemplary embodiment into its inner cavity H 1 protrudes. In Fig. 9, the sensor assembly 5, 6 and the tubular body 1 assume this relative position. A melting device 22, in the exemplary embodiment a burner, is used for joining.

[0058] With the pipe body 1 clamped, a measurement is taken to determine the exact position of the front opening 1a. The chuck 15 can then be rotated. The melting device 22 moves from a starting position into a joining position according to the measurement of the position of the opening 1a. Before the actual joining, for example, in the Fig. 9, the tubular body 1 is heated by the melting device 22 via its front peripheral edge surrounding the opening 1a. The peripheral edge begins to melt, and the opening 1a narrows. The suction gripper 13 moves the sensor assembly 5, 6 in the longitudinal direction L until it touches the already softened peripheral edge of the opening 1a.

[0059] If the pipe body 1 is to be in the cavity H iWhen joining, a negative pressure is applied so that the sensor assembly 5, 6 adheres to the peripheral edge of the opening 1a, the tubular body 1 or only the cavity H I at its rear end with a seal. Sealing is preferably performed before the tubular body 1 is set in rotation. Sealing is also advantageous for quality control purposes after joining. After joining, the tubular body 1 can be pressurized while still in the chuck 15, or optionally at another location, to create the fusion joint S. 1 to check for leaks.

[0060] Fig. Figure 10 shows the joining arrangement of tubular body 1 and sensor assembly 5, 6 with the sensor material body 5 already attached to the tubular body 1. For melting and joining, it is advantageous if the tubular body 1 rotates about its longitudinal axis L. The gripper 13 can be rotatably mounted and remain on the sensor material body during rotation of the tubular body 1. However, it is more expedient if the gripper 13 detaches from the sensor material body 5 immediately before the onset of rotation, so that the sensor assembly 5, 6 can rotate freely from the gripper 13 together with the tubular body 1. In this case, it is advantageous if the sensor group 5, 6 is held to the tubular body 1 by applying negative pressure to the latter. The rotation centers the sensor assembly 5, 6 on the tubular body 1. When the melt connection S 1 is established, the melting device 22 moves back to the starting position.

[0061] After joining, S can be used to check the fusion joint.1Overpressure is generated and monitored in the tubular body 1. If a pressure drop is detected, the assembly comprising the tubular body 1 and the joined sensor assembly 5, 6 is rejected as defective. If no pressure drop is detected, the assembly 1, 5, 6 is moved to the next process step. For this purpose, the rotation of the chuck 15 is stopped if the chuck 15 was previously rotating, the chuck 15 is opened, and a gripper pulls the assembly 1, 5, 6 out of the chuck 15 and places it on a transport device, for example a conveyor belt. The transport device moves the assembly 1, 5, 6 one position further to create a free space for the next assembly 1, 5, 6.The machine cycle begins again and continues until either the transport means is filled, a supply magazine for pipe bodies 1 is emptied or the wire reel for producing line pieces 6 or the strip material for producing sensor material bodies 6 is used up.

[0062] In a subsequent process step, the line section 6 of the respective assembly consisting of the tubular body 1 and the sensor assembly 5, 6 is electrically connected to the connecting line 7 ( Fig. 1 and Fig. 2) connected.

[0063] Fig. 11 shows an assembly 1, 5, 6 in a joining position for establishing the frictional connection. A chuck or gripper 16 holds the assembly 1, 5, 6 in the joining position. The connecting cable 7 and a shrink tube 8 are inserted into the tubular body 1 through the open rear end of the tubular body 1 and advanced in the longitudinal direction L toward the sensor assembly 5, 6 until the connecting cable 7 and the shrink tube 8 overlap the cable section 6 lengthwise and the shrink tube 8 surrounds the cable section 6 and the connecting cable 7. This positioning of the connecting cable 7 and the shrink tube 8 is carried out using an auxiliary tool 23.

[0064] The Fig. 12 next to the heat-shrink tubing 8 is designed as a tube, for example a glass tube. The heat-shrink tubing 8 is received in a front receiving section 24 of the auxiliary tool 23 when inserted into the tube body 1, i.e. the heat-shrink tubing 8 is shaped so as to be adapted with respect to its outer circumference and the auxiliary tool 3 is shaped so as to be adapted with respect to its inner circumference, at least in the receiving section 24, so that it can receive and hold the heat-shrink tubing 8 with a slight frictional connection. It is advantageous if the heat-shrink tubing 8 protrudes beyond the front end of the auxiliary tool 23 when received. In order to receive the heat-shrink tubing 8 in a defined manner, for example to prevent it from slipping into the hollow auxiliary tool 23, an axial stop 25 for the heat-shrink tubing 8 is formed in the front end section of the auxiliary tool 23.In the exemplary embodiment, the auxiliary tool 23 is narrowed in the front end section, so that the receiving section 24 for the shrink tube 8 and the axial stop 25 are formed there. The connecting cable 7 expediently extends through the auxiliary tool 23 and the shrink tube 8 when inserted into the tubular body 1.

[0065] In Fig. 13, the auxiliary tool 23, together with the connecting cable 7 and the heat-shrink tubing 8, is inserted into the joining position of the tubular body 1. It can be seen that the auxiliary tool 3 is adapted in terms of its outer diameter to the inner diameter of the inner tube 3 of the tubular body 1, so that it is guided axially by the inner tube 3 during insertion.

[0066] The entire assembly comprising assemblies 1, 5, 6, the connecting cable 7 overlapping longitudinally, the shrink tubing 8 overlapping longitudinally, and the inserted auxiliary tool 23 is placed in an oven, expediently together with other such assemblies. In the oven, the assembly or multiple assemblies are heated so that the respective shrink tubing 8 shrinks and presses the connecting cable 7 longitudinally against the cable section 8 in the overlap, thereby establishing contact.

[0067] In subsequent process steps, the reference electrode is manufactured, the connecting line 7 and a connecting line of the reference electrode are connected to a connecting device at the rear end of the tubular body 1, and the tubular body 1 is closed by means of the connecting device. Reference symbols: 1 pipe body 1a front opening 2 outer tube 3 inner tube 4 Diaphragm 5 Sensor material body 6 line section 6a first line section 6b second line section 7 Connection cable 8 shrink tubing 9 - 10 joining holder, receiving tray 11 first gripper 12 second gripper 13 third gripper 14 - 15 chucks 16 chucks 17 Vacuum line 18 Vacuum line 19 Vacuum line 20 joining tools, welding tools 21 - 22 Melting device, burner 23 Auxiliary tools 24 Recording section 25 Axial stop, constriction D 5 largest width, diameter of the sensor material body 5 H A outer cavity H I inner cavity L Longitudinal axis, longitudinal direction L1 Length of the pipe body 1 L 6 Length of the line section 6 S 1 Fused connection S 2 Material closure

Claims

[1] Method for producing a measuring electrode for electrochemical measurements in a measuring fluid, in which (a) a sensor material body (5), from which a line piece (6) made of electrically conductive material, which is electrically conductively connected to the sensor material body (5) protrudes, is joined to the tubular body (1) so that the line piece (6) protrudes into the tubular body (1) in the joined state, (b) a connecting cable (7) made of electrically conductive material is inserted into the pipe body (1) until it overlaps with the cable section (6), and (c) the connecting cable (7) is connected in the overlap in a force-fitting electrically conductive manner to the cable section (6), (d) wherein a shrink tube (8) is inserted into the pipe body (1) so that the shrink tube (8) surrounds the line piece (6) and the connecting line (7) in the overlap, and (e) the shrink tube (8) is shrunk so that the shrunk shrink tube (8) presses the cable piece (6) and the connecting cable (7) together lengthwise and thereby connects them in an electrically conductive manner. [2] Method according to the preceding claim, in which - a tubular auxiliary tool (23) is inserted into the tubular body (1) which is open at a rear end and is moved in the direction of the sensor material body (5), - wherein the auxiliary tool (23) surrounds the connecting cable (7) and the shrink tube (8), - the connecting cable (7) and the shrink tube (8) are brought into overlap with the cable piece (6) by means of the auxiliary tool (23), so that the shrink tube (8) surrounds the cable piece (6) and the connecting cable (7) in the overlap, and - the shrink tube (8) is shrunk in the overlapping state, so that the shrunk shrink tube (8) presses the cable piece (6) and the connecting cable (7) together lengthwise and thereby connects them in a force-fitting, electrically conductive manner. [3] Method according to one of the preceding claims, in which the arrangement of tubular body (1), sensor material body (5), line piece (6), connecting line (7) and shrink tube (8) and optionally auxiliary tool (23) is heated in an oven and thereby the shrink tube (8) is shrunk so that the shrink tube (8) presses the line piece (6) and the connecting line (7) lengthwise against one another. [4] Method according to one of the preceding claims, in which - the tubular body (1) has a front opening (1a) at a front measuring end, - the sensor material body (5) is arranged at the measuring end of the tubular body (1) so that the line piece (6) projects through the front opening (1a) in the longitudinal direction (L) of the tubular body (1), and - the tubular body (1) is heated in the region of the front-side opening (1a) and is joined fluid-tightly to the sensor material body (5) around the front-side opening (1a) by means of a fusion connection (S1). [5] Measuring electrode for electrochemical measurements in a measuring fluid, the measuring electrode comprising: 1.1 a tubular body (1), 1.2 a sensor material body (5) arranged on a front tubular body region of the tubular body (1), 1.3 a line piece (6) which is electrically connected to the sensor material body (5) and projects from the sensor material body (5) into the tube body (1) in the longitudinal direction (L) of the tube body (1), and 1.4 an electrically conductive connecting cable (7) extending in the tubular body (1) towards a rear region of the tubular body (1), characterized by , that 1.5 the connecting cable (7) overlaps the cable section (6) lengthwise and is electrically connected to the cable section (6) by means of a frictional connection, and 1.6 a shrink tube (8) surrounds the cable section (6) and the connecting cable (7) in the overlapping area and, in the shrunken state, presses them together lengthwise and thereby connects them in an electrically conductive manner. [6] Measuring electrode according to the preceding claim and manufactured by the method according to one of claims 1 to 4. [7] Measuring electrode according to one of the two immediately preceding claims, wherein the line piece (6) has a first line section (6a), preferably end section, a second line section (6b), preferably end section, and a transition section connecting the line sections (6a, 6b), in the first line section (6a) is connected in an electrically conductive manner, preferably by a welded connection (S2), to the sensor material body (5) and in the second line section (6b) is connected in an electrically conductive manner to the connecting line (7) by means of the shrink tube (8) and is angled in the transition section. [8] Measuring electrode according to one of the three immediately preceding claims, wherein the sensor material body (5) and the line piece (6) are welded directly together. [9] Measuring electrode according to one of the four immediately preceding claims, wherein the tubular body (1) has a length L1 and the line piece (6) measured on the sensor material body (5) has a length L6 with L6 < L1 / 5 or L6 < L1 / 10. [10] Measuring electrode according to one of the five immediately preceding claims, wherein the sensor material body (5) in plan view of an end face has a maximum width D5 overall and the line piece (6) measured on the sensor material body (5) has a length L6 with L6 < 6·D5 or L6 < 3·D5. [11] Measuring electrode according to one of the six immediately preceding claims, wherein the measuring electrode and a reference electrode form a single-rod measuring chain. [12] Measuring electrode according to one of the seven immediately preceding claims, wherein the tubular body (1) and the sensor material body (5) are connected by means of a fusion connection (S1).

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